Palomar Testbed Interferometer

The Palomar Testbed Interferometer (PTI, depicted here on the right) is a near-IR, long-baseline stellar interferometer located at Palomar Observatory in north San Diego County. It was developed primarily to demonstrate the utility of ground-based differential astrometry in the search for planets around nearby stars, and to develop key technologies for the Keck Interferometer and space-based missions.

PTI's dual-star tracking system, the first and (still) only of its kind, simultaneously tracks interference fringes from a target star and a reference star against which the target is measured.

PTI has also been used to measure the sizes of dwarf, giant, and supergiant stars; the sizes of emissive regions around young stellar objects; and binary star orbits. It is the first interferometer to have directly measured the diameter changes of a Cepheid variable star, and directly measured the rotational oblateness of a rapidly rotating star.

NExScI personnel have been instrumental in the development and scientific accomplishments of PTI, and are largely responsible for its data infrastructure and science planning and processing applications.

PTI is no longer an operating facility, but previously collected data can be accessed through the PTI archive. The PTI support page describes the observing modes and data reduction process.

PTI links

• NExScI support for PTI, including the publically available PTI data archive.
• A brief picture tour of PTI.
• Publication list